Chloropleth maps with Mapserver

[Stephen Woodbridge]

Jason Pickering wrote:
> Hi Bill,
> Well, the end maps are more or less the same. I think the best
> examples of what I would like to do can be found at the KIDS website.
> 
> http://kids.fao.org and then under "Application Examples".
> Another good example is at
> http://www.fao.org/landandwater/agll/agromaps/interactive/index.jsp
> 
> I am not starting with individual points (well, maybe but the data has
> already been aggregated).
> 
> The question for me is whether it would be easier to modify KIDS (also
> open source) or Mapserver to accomplish what I would like to be done.
> I agree, that it seems that it in principle should be able to be
> accomplished with Mapscript. It seems less obvious to me how to
> implement this functionality in KIDS, as it doesn't have the same sort
> of scripting support as Mapserver. I agree that there may be a way to
> do it, but I thought if someone has proven that it can be done, it
> would be good to start there instead of coding from scratch.

Yes it can be done. I've done it without mapscript
http://imaptools.com/~woodbri/thematic/thematic.cgi?name=ThemeMap&cmd=Map&debug=&location=MA&method=kmeans&numclasses=10&demographic=DP40063
It would be better with the COLORRAMP support or if I played a little 
more with mapscript or the mapfile.

I does require using postGIS.

-Steve W.

> I will checkout the developers mailing list as well to see what is
> there. Thanks for the tips.
> 
> Best regards,
> JPP
> 
> 
> 
> 
> 
> 
> On 10/2/05, Bill Binko <bill at binko.net> wrote:
> 
>>I assume you mean Choropleth Maps like this article suggests:
>>
>>http://www.teachingideas.co.uk/geography/chlormap.htm
>>
>>Are you (like the article) starting with points and you want to group
>>them?  That is, you want the user to be able to specify how many groups to
>>create, but there is underlying data?
>>
>>There may be a way to do this in Mapscript.  Also, you might find
>>gdal_contour of value (or something similar).
>>
>>Bill
>>
>>On Sun, 2 Oct 2005, Jason Pickering wrote:
>>
>>
>>>I am currently evaluating the capabilities of MapServer to retrieve
>>>data from a Postgresql database and display it on a chlorpleth map.
>>>For instance, I have data like:
>>>
>>>Area      IndicatorValue
>>>
>>>Area 1     10
>>>Area 2    20
>>>Area 3  15
>>>Area 4  20
>>>etc etc
>>>
>>>Each region will be represented by a color, depending on what the
>>>value is in the "IndicatorValue" column. The users need to be able to
>>>select (dynamically) how many color regions will be displayed on the
>>>map, and what the value range of each color is.
>>>
>>>I have searched high and low through the archives, and Google, but
>>>can't seem to find a definitive answer, or better yet, and example of
>>>how this can be done with Mapserver.Any pointers would be most
>>>welcome.
>>>
>>>Best regards,
>>>JPP
>>>
>>>
>>
>